Flotation concentrator



J. M. PATEK FLOTATION CONCENTRATOR Jan. 3, 1939.

A'roRNEY Patented Jan. 3, 1939 UNITED `l STATES PATENT oFF-ICE `2 Claims.

This invention relates to otation machines of the class known as pulp body machines and constitutes a distinct improvementI over machines of the above described class heretofore known in that a concentrate may be obtained with the machine of this invention which is richer in the desired ore and poorer in entrapped, contaminating gangue substances. The apparatus of this invention comprises an enclosure for a .body of pulp, the enclosure being so arranged that the pulp may circulate across the bottom of the en` closure, up one side of the same, and thence in a generally horizontal direction across the free surface,` the latter flow being impeded and modied by one or more inverted weirs which dip beneath the free surface dividing said surface into two or more areas, the pulp then returning to the bottom of the enclosure so that the circulation thereof will be repeated. Circulation may be induced by means serving also to draw in the necessary air to create pulp body conditions. although any means for inducing circulation andintroducing air under pulp body conditions may be employed.

The employment of the pulp body principle in various types of flotation machines has been extensive and successful. However, in all of the machines heretofore known or used, pulp body conditions have been created in the lower portion of a flotation cell by supplying air through a mechanical means which subdivides the air and produces in the pulp momentary pressure changes which are conducive to solution of the air. The pulp upon escaping from the locality of the pressure influences noted above, is in a condition of .supersaturation with respect to dissolved air. The dissolved air, according to well known printuples, does not become released spontaneously, but requires a solid-liquid interface to provoke its withdrawal from solution. The myriads of pulp particles afford such interface and air is precipitated directly upon the pulp particles. Air, of course, is precipitated alike upon ore and gangue particles, but if the ore particles have been selectively conditioned by the proper reagents the adherence of the air thereto far eX- ceeds the adherence of the air to unconditioned gangue particles. All of the air thus released Within the apparatuses heretofore known is per- Initted to rise and to create a froth upon the free surface of the cell. The froth thus produced is impoverished by all of the barren air, or air which may have been able to lift gangue material simply by entrainment. The bulk of the froth thus produced is far in excess of that necessary to hold the separated ore mineral. This increased bulk augments the proportion of gangue material whicnmay be held by'the froth simply by mechanical entrainment.

In the machine of this invention the..gain-in the quality and effectiveness of the froth is ob'- tained by taking advantage of the dilierence in velocity of rise of barren air and ore-laden air. As explained above, in the pulp body action ap- 5 preciable quantities of air are precipitated upon unconditioned gangue material. The air thus precipitated is not held by any reagent and therefore quickly frees itself from the gangue. This air, if permitted to rise freely to an open 10 surface, will escape with very little tendency to form a froth. In the apparatus of this invention a very substantial proportion of the barren air is permitted to rise to a free surface and to escape without the formation of froth. The more slowly l5 rising ore-laden air, however, is swept beneath the inverted Weir and then permitted to rise to form a froth, which froth is inatedlittle beyond the bulk necessary to support the separated ore.

The apparatus of this invention 4is best de- 20 scribed by reference to the accompanying drawing, wherein Fig. 1 represents a cross-sectional view of a flotation cell in operation, and

Fig. 2 is a detailed cross-sectional view of the 25 mechanical means employed to induce circulation and introduce air under pulp body conditions.

As shown in Fig. 1, an apparatus embodying this invention may be constructed of an opentopped, boxlike enclosure having end walls I and 30 2, with a bottom 3 and sides 4 completing the enclosure. Through the end wall 2 a diffuser cone 5 enters. Communicating with the diffuser cone 5 is an air inlet pipe 'I containing an aircontrol valve 8 and secured to the diffuser cone 35 is a stuffing-box 6 through whichA a shaft 9 enters. Mounted upon the shaft 9 and within the diffuser cone is a rotor cone I0, thelatter construction being shown more in detail in Fig. 2. The cone I0 is secured to the shaft 9 so that it 40 will rotate therewith. Also secured to shaft 9, and in the position indicated, is an` impeller II, the same being composed of a plurality of angular blades I2 mounted upon a relatively large hub I3. Surrounding the impeller is a cylindri- 45 cal shroud I4 which, as shown in Fig. 1, may be lined with directing vanes I5. The above described means are for the introduction of air and the 'creation of the pulp body condition and are of the type disclosed in my copending applica- 50 tion, Serial No. 743,923, the mechanical details of which, however, are not essential for the obtaining of the desirable result of this invention. Any suitable means for the introduction of air -and the 55 cration of pulp body condition may be employed.

'Reaching from 'the bottom 3 to the end wall I is a curved deector .I6 for the purpose of direct..- ing the discharge from the impeller Il forwardly in a uniform manner, as indicated by the arrows.

273 which discharges behind the impeller II.

Submerged within the cell in an inclined position is a baflle I1, which aids in securing the generally horizontal ow of uid across the top of the cell. Dipping below the free surface of the pulp in the cell and in a direction generally transverse to the flow of the pulp is an inverted Weir I8, which divides the upper surface of the pulp into areas I9 and 20. The end wall 2 is terminated at a lower level so that the walls bounding the area constitute an enclosure having a lip 2I over which froth may escape into a launder 22. Untreated pulp is fed into the machine through a conduit A continual discharge of pulp is removed through a conduit 24, which passes out of the cell through the side wall 4 and rises to form a siphon, as indi- .cated by dotted lines 25. The siphon is in .communication with a. vent seal 26 which is provided with an adjusting sleeve 21 so that the level of the same may be placed at the point desired. When the pulp level within the cell 4is high enough to close the vent seal 26 the siphon 25 functions towithdraw pulp from the cell through the conduit 24 until the pulp level is lowered sufiiciently to break the seal of the vent seal 26. The discharge of material through the siphon 25 permits the removal of material of a 'coarse nature, due to the fact that the siphon can be connected to the lower portion ofthe enclosure and a relatively high rate of flow is established during discharge. This permits the discharge of material coarser and heavier than the heaviest material that can be floated.

As shown in Fig. 2, the impeller II draws a cylindrical flow of fluid around the outside of the diffuser cone 5 and at the same time, as shown by the arrows, the relatively large hub I3 produces a certain amount of short-circuiting of flow, permitting a backward flow of fluid which sweeps into the rotor cone I0, and thence outward along the inner face of the diffuser cone 5, joining the cylindrical flow which is passing over the outer portion of diffuser cone 5. Reduced pressure at the back of the impeller therefore draws air through the inlet pipe 1 and over the rotor cone and into the uid in the direct vicinity of the blades I2. The regulation of the quantity of air admitted is accomplished by the adjustment of valve 8. In the machine of this invention air regulation is thus completely subject to control, inasmuch as the air admitted through valve 8 is the only air which can enter the circulation of the pulp. 'I'he impact of the rapidly moving blades creates a local momentary increase of pressure right at the point where the air is being introduced. A considerable quantity of air goes into solution under this increased pressure. As the pulp leaves the shroud I4, or during its passage therethrough, this momentary pressure is relieved and air coming out of solution upon the pulp particles produces a typical pulp body action. As the iiuid flows toward the end wall I and beneath the submerged baffle I1, air, which is pre- 'cipitated upon unconditioned gangue particles,

has a tendency to free itself and to rise. Air, however, which is precipitated upon conditioned ore particles cannot release itself from the ore par ticles and the apparent density of this air being thus increased, its rising tendency is diminished with respect to barren air. As the fluid reaches the end wall I its direction of flow is reversed and during a portion of the flow from end wall I to the inverted Weir I8 a considerable quantity of the barren air, due to its increased tendency to rise,

escapes through the free surface of the pulp in the area I 9. As the length of travel increases, however, the slower rising air which is attached to ore particles finally makes its way upwardly to the surface and accumulates in the area 20. The separation produced by the inverted Weir I8 is not completely selective and a small amount of froth, as shown in the drawing, will rise in the area I9. The loss due to this, however, is more than offset by the quality of froth obtained in the area 20 and no escape of ore or reagent is entailed in this action. In fact, some of the froth accumulating in area I9 is periodically drawn under the inverted Weir I8 by the sweep of the current and the remainder of it is broken up and the ore returned to the cycle for further treatment simply by the normal action of turbulence in the cell. The froth collecting in area 20 has been found to carry a higher proportion of ore per unit volume of froth than is obtained in machines heretofore used. Furthermore, due to the high concentration of cre per unit volume of froth, the mechanically entrained gangue material is present in smaller proportion to the ore than is the case in machines heretofore known and used.

This invention has been described in connection with one particular embodiment thereof. It is intended, however, that the protection of Letters Patent to be granted thereon be not unnecessarily limited thereby, but extend to the ilow generally parallel to the upper free surface of said pulp, and means including an inverted weir extending below the liquid level of said pulp, for dividing said upper free surface into an area for the escape of barren gas and an area for the collection of ore-laden froth and consisting of a barrier extending from side to side across the top of said inclosure and across the general direction of circulation of said circulating body of pulp and extending above and below the upper free surface of said body of pulp.

2. In an apparatus for froth flotation, the combination comprising an enclosure for holding a body of fluid pulp, means for introducing air into said enclosure at a submerged point, means forming an upper free surface of the pulp into which barren air may escape, means forming an upper free surface of the pulp where froth may collect, means including an inverted Weir dividing said aforesaid air escaping surface from said aforesaid froth collecting surface and consisting of a barrier extending from side to side across the top of said enclosure and extending above and below the surface of said body of fluid pulp, and mechanically driven means separate from said means for introducing air into said enclosure and controllable independently of said means for introducing air for causing said pulp to flow f irst beneath said air escaping surface and then beneath said froth collecting surface. 

